With just two innocuous tweets on Feb. 1, the billionaire hedge fund manager appeared to accumulate more than 2,000 followers. The photo looked good. The people he followed were sober financial news sources. The link went to the real Appaloosa Management website.

The Tepper-does-Twitter fakeout raises an important question about what's real and what's not on the micro-blogging platform.

@Carl_C_Icahn is of course the real Carl Icahn, the billionaire activist investor and chairman of Icahn Enterprises. His tweets still have the power the move a stock's price and Icahn has amassed more than 141,000 followers since first tweeting about Dell on June 20, 2013.

One giveaway that Icahn is real is the blue check symbol next to his name, meaning Twitter has verified the account as legitimate. The fake Tepper account had no such official stamp of approval.

But Twitter can be tricky. David Einhorn's twitter account is unverified but real: @davidein. But the Greenlight Capital founder only tweets about charity and poker. He still has nearly 16,000 followers. A spokesman for Einhorn declined to comment on the account.

Not all hedge fund managers have followings proportional to their investment stature.

One is Jaffray Woodriff, the chief executive officer of $3.3 billion Quantitative Investment Management (@JaffrayW, 2,572 followers). A second is Tom Steyer, the founder of more than $19 billion Farrallon Capital Management (@TomSteyer with 2,621 followers). Steyer's tweets reflect his new focus on environmental activism. A third is John Brynjolfsson, chief investment officer of $925 million Armored Wolf (@Brynjo, 1,381 followers).